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The pins on tegra are controlled by three different units, the pinmux, the
pin group controls, and the GPIO banks. Each of these units controls some
aspect of the pins, and they layer together and interact in interesting ways.
By default, the GPIOs are configured to pass through the special purpose IO
that the pinmux is configured to and so can be ignored unless a GPIO is needed.
The pinmux controls which special purpose signal passes through, along with
pull ups, downs, and whether the output is tristated. The pingroup controls
change the parameters of a group of pins which all have to do with a related
function unit.
The enum which holds constants related to the pinmux is relatively involved
and may not be entirely complete or correct due to slightly inconsistent,
incomplete, or missing documentation related to the pinmux. Considerable
effort has been made to make it as accurate as possible. It includes a
constant which is the index into the pinmux control registers for that pin,
what each of the functions supported by that pin are, and which GPIO it
corresponds to. The GPIO constant is named after the GPIO and is the pinmux
register index for the pin for that GPIO. That way, when you need to turn on
a GPIO, you can use that constant along with the pinmux manipulating functions
to enable its tristate and pull up/down mode in addition to setting up the
GPIO controls.
Also, while in general I prefer not to use macros or the preprocessor when
writing C code, in this case the set of constants in the enums was too large
and cumbersome to manage without them. Since they're being used to construct
a table in a straightforward way, hopefully their negative aspects will be
minimized.
In addition to the low level functions in each driver, the GPIO code also
includes some high level functions to set up input or output GPIOs since that
will probably be a very common thing to want to do.
Old-Change-Id: I48efa58d1b5520c0367043cef76b6d3a7a18530d
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://chromium-review.googlesource.com/171806
Reviewed-by: Ronald Minnich <rminnich@chromium.org>
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit 5cd9f17fe0196d13c1e10b8cde0f2d3989b5ae1a)
tegra124: Add base address for the pinmux and pingroup registers.
There weren't any constants for the pinmux or pingroup registers in the
address map header.
Old-Change-Id: I52b9042c7506cab0bedd7a734f346cc9fe4ac3fe
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://chromium-review.googlesource.com/172081
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit 79b61016bfd702b0ea5221658305d8bd359f4f62)
Squashed two related commits.
Change-Id: Ifeb6085128bd53f0ef5f82c930eda66a2b59499b
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Reviewed-on: http://review.coreboot.org/6702
Tested-by: build bot (Jenkins)
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